1. Field of the Invention
The present invention relates to a shutter-time-perference single lens reflex camera containing a magnet release device.
2. Description of the Prior Art
For a camera which can effect automatic exposure, automatic winding up, automatic photographing, remote photographing, cameramanless photographing, etc., the shutter time preference system is generally adapted for the following reasons (1) and (2).
(1) As the shutter time is constant, more frames can be continuously photographed if the shutter speed is preset at a predetermined time (for example 1/2000 second).
(2) In the case when continuous photographing is to be done with a constant cycle, it is easier to maintain a constant photographing interval because the shutter release time is constant.
However, in the conventional shutter-time-preference cameras, the push-down of the release button is transferred to various members through mechanical association to effect the diaphragm control, mirror-up, running of the front screen etc. Therefore, because of the mecanical transference, the release button has necessarily a long stroke and heavy weight so that shutter oscillation is caused more often and delay in photographing time is caused. Also in the conventional camera, the arrangement of the release button is restricted by the structure of the association mechanism, so that it can not be always arranged in the best position for photographing.
Further, in the case when an electric driving device is attached to the conventional camera, further mechanical association is required, thus causing a complicated structure of the electric driving device due to remote operation, etc. and also the arrangement of the electric driving device is restricted.
Further, in the electric driving device itself, various systems such as a system which detects change in the winding-up torque, a system which detects change in the winding-up speed, and a system which detects the winding-up angle have been used for detecting completion of winding-up action of a shutter charge etc., but these systems all require a single-purpose detecting means (for example, a torque detecting means in the system which detects change in the winding-up torque), and in case of the system which detects change in the winding-up torque or change in the winding-up speed, the detecting means is arranged in the electric driving device, thus requiring a large space. This has been a large problem prohibiting minimization of the size of the electric driving device. On the other hand, in case of the system which detects the winding-up angle, only a contact piece is required as detecting means on the winding-up shaft and the shutter shaft etc. in the camera body and thus it has advantage in simplification of the structure. However, this system has defects that when the winding-up mechanism is stopped during the winding-up action due to absence of the film for example, it is impossible to detect it, so that the winding-up motor is imposed with excessive load and gets out of order, or some structural members of the winding-up mechanism are broken.
Also, when the camera is driven by the electric driving means, means for detecting the completion of exposure is required other than the means for detecting completion of the winding-up action, namely means for producing a signal for starting the winding-up action. In the conventional cameras, means for detecting completion of exposure is provided separately from the means for detecting completion of the winding-up action, and this causes a problem against the minimization of the device size and reduction of production cost.
One of the objects of the present invention is to overcome the above problems, and for this object, a camera starter provided in the camera body is actuated by a magnet means also provided in the camera body, so as to effect diaphragm control as well as shutter control.
Another object of the present invention is to transfer signals between the camera body and the electric driving device without contacts.
Still another object of the present invention is to control opening and closing of the driving circuit of the electric driving device by means of a safety switch controlled by the action of the shutter rear screen.